Gear Unsafe Emergency today!! So why did this part break/shear?

[THill182]

Today I had my first real emergency in my Ovation in 14 years or so of flying it (2000 Ovation II, with 310 HP upgrade). In short, coming in for a landing I put the gear down -- heard an "unusual clunk" -- and then the Gear Unsafe warning started blinking.

Long story short, the FBO confirmed that the gear was down during a fly-by, the green "thing" inbetween the seats appeared to be aligned (gear-down), but not illuminated (since the gear was unsafe).

I landed with the firetruck ready to role, but the landing was thankfully uneventful.

My questions:

(1) What happened? I am attaching three pictures of a broken "tube"/rode under the plane -- looks like it just sheared off. I am attaching pictures of the tube that broke, in the center underneath the plane.

(2) What specific part is that in the Parts Catalogue? It looks like part of the Retraction System - Landing Gear; but it happened during extension of the gear.

(3) Any ideas what can cause this?

I hope the shop at the airport at FNL can fix this before I need to return home...As a (BIG!) side note: They were incredibly busy but started to look at it immediately. General aviation will just die when businesses and their kind owners finally retire without replacement....

[jackn]

Looks like it’s ‘just’ a rod end sheared. That is an easy fix. My guess is the down & locked relay failed and the motor kept going till the breaker finally popped( check it out). Fortunately for you, the landing gear was down and locked by the over center. I wouldn’t try to move the plane though. 

[KSMooniac]

I don't any idea how you could break the rod end bearing like that! Could just be unlucky with a bad part. It looks like the paint is rubbed off that rod...I wonder if that was done prior to the failure or after.

I bet the rod end and rod are easily sourced thru a MSC so I'd call your favorite one for starters and get the parts headed to the FBO. Your rod may or may not be bad, but you likely can't tell until removing it for inspection. Hopefully that FBO has the service manual, parts catalog, and rigging tools. You'll need to swing the gear to verify everything of course after replacing that tube.

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[N201MKTurbo]

I would say either it overran the limit switch, or the preloads were out of whack for a long time and every cycle was over stressing the rod until it finally stress fractured.

[jackn]

3 minutes ago, N201MKTurbo said:

or the preloads were out of whack for a long time and every cycle was over stressing the rod until it finally stress fractured.

That would account for the paint rubbed off on the bottom of the tube. 

[Guest]

2 hours ago, THill182 said:

Today I had my first real emergency in my Ovation in 14 years or so of flying it (2000 Ovation II, with 310 HP upgrade). In short, coming in for a landing I put the gear down -- heard an "unusual clunk" -- and then the Gear Unsafe warning started blinking.

Long story short, the FBO confirmed that the gear was down during a fly-by, the green "thing" inbetween the seats appeared to be aligned (gear-down), but not illuminated (since the gear was unsafe).

I landed with the firetruck ready to role, but the landing was thankfully uneventful.

My questions:

(1) What happened? I am attaching three pictures of a broken "tube"/rode under the plane -- looks like it just sheared off. I am attaching pictures of the tube that broke, in the center underneath the plane.

(2) What specific part is that in the Parts Catalogue? It looks like part of the Retraction System - Landing Gear; but it happened during extension of the gear.

(3) Any ideas what can cause this?

I hope the shop at the airport at FNL can fix this before I need to return home...As a (BIG!) side note: They were incredibly busy but started to look at it immediately. General aviation will just die when businesses and their kind owners finally retire without replacement....

I would assume item 24 rod end bearing for both left and right push rods.

Clarence

[THill182]

Thanks everyone! Part is on order and should get here in the morning. Also I talked with Don Maxwell who has been doing my annuals for a few years, and he also suggested to look at and preferably replace both rods. I will ask tomorrow morning if that's still possible.

Was a scary experience. I guess I came very close to a "BIG PROBLEM" had the gear collapsed....

[carusoam]

Great report, THill.

Thanks for sharing the details and pics.

Good luck getting all the details sorted.

Best regards,

-a-

[Cyril Gibb]

Feedback, once you know what it was, would be valuable.  If it was misrigged at the factory, owners of this plane vintage might have the same issue.

[Guest]

1 hour ago, Freemasm said:

I looked at this on a computer today versus a phone yesterday. Something appears way off in your rigging. I assume the gear was actuated to a safe condition (all three locked over-center). That said, I don't see where either limit switch is actuated in your photos. This would certainly be an issue (at least a contributor) as the actuator would keep driving; subsequently, linkage springs would collapse, stresses would exceed their design points, etc. I will say I'm surprised it was only the rod end versus the long linkage when loaded in compression. I'd be very careful when inspecting to assure that these linkages are not deformed. The slightest non-concentricity in a column that long could be an issue. The other surprise to me is why the gear circuit breaker wasn't popped before the linkage was damaged as someone previously mentioned. Had it popped previously? The person who's done your annuals is well respected but I'd consider a third party with appropriate Mooney experience to investigate. All that said, this could have ended up way worse.  Please keep us informed. There's probably a valuable lesson in this.  Best of luck. 

Unless I’m missing something, the up limit switch won’t be tripped as the gear is down and the tab on the rod is nowhere near it?  The down limit tab may be in contact with the limit switch if the rod is held in the correct place.

I’d guess that the actuator ball nut has run into the mechanical stop plates when the limit switch didn’t stop the motor, meaning the other tube as you suggest in under extra compressive load.

Clarence

[MARZ]

I'd take a quick look at the top of the tubing that the bottom of the rod was rubbing on as well just for grins....... 

[Chris K]

Subscribing to this thread since I also own a 2000.  Interested in what is found to be the issue.

[THill182]

Well, the plot "thickens":

1. The first picture shows the broken rod end; the second picture shows the same part installed for the other side(not broken); notice the grove on the side of the threading, and how is used to hold a safety clip.

2. The tube itself is part 915053-501; the Rod End part is actually MM-4M-13 (thank you Stacey Ellis!).

3. BUT: That part does not have the grove! See below:

4. According to Stacey Ellis, this part has never been modified and no "safety clip" has ever been used on Ovations.

I am no engineer but it seems to me that putting a grove into such a part will not exactly strengthen it. Note that this plane has had early damage in 2000 that was repaired at the factory (long story short, the fuel system setup was wrong, and on touch-and-go the first owner ran off the runway on takeoff when the engine quit; a new Service Bulletin came from that accident if I remember correctly; I have had the plane for 16 years or so (more?), and have not had any issues with the gear ever)

So my question at this point is: Does anyone know if in other 2000 Ovations there is a "grove" in this part?

Anyway, I consider myself extremely lucky that the gear didn't collapse! Also, I decided to stay perhaps another day and have both rods replaced (since the other one also has a part we don't know) by the very nice/accommodating shop who was the one who figured all this out! .

Really strange! Anyway, hopefully, this is the end of my gear troubles...

 

 

 

[takair]

It is strange that the tube has notches for the clip.  It also seems provisioned such that the nut is safeties to the clip.  I wonder where (if) you would safety the new link?  That really is an odd situation.

[ArtVandelay]

This sounds like a question for Lasar folks or Maxwell.

[THill182]

29 minutes ago, teejayevans said:

This sounds like a question for Lasar folks or Maxwell.

Funny you should say that... Turns out the discussions regarding the part (that the shop here initiated) involved Lasar -- they shipped the part MM-4M-13; which the shop thought was wrong; Lasar then communicated with Stacey Ellis at Mooney who emailed back that this part never changed (so no groves and clip). I also asked them to run it by Don Maxwell, and he too apparently (I was told) agreed that he had never seen any other part than the one that Lasar had shipped (without the grove). So either somebody at some point early in the planes life put a different part in (which has the same number printed on it I think, it looks like that in the picture; I'll confirm), or in 2000 a different part was actually in use when the plane was built (Stacey Ellis said that was not the case). Really a riddle.

I'll also find out how the safeties are tied to the nut, and can provide more detailed pictures of the broken part.

[THill182]

30 minutes ago, Freemasm said:

@THill182 can you get your hands on the failed parts?  Meeting a Non-Destructive Test Engineer today for lunch. I'll ask if he can do a quick look at the fracture surface in his lab. Could prove interesting and/or beneficial. Let me know. 

Sorry, not until Monday when the new parts will be installed; but my plan is to then take detailed photos of the actual fracture. Really appreciate your offer though! I am confused here also. One question I have: If you put a "groove" into the threading/bolt -- will that not weaken it? If that is a critical and stressed part -- and if for sure today Mooney does not put that part in -- that seems "not right" and a potential higher probability failure point....

[THill182]

PS: As I keep digging I also found a SB from 2002 applicable to M20R's of my serial number, relating to these very parts (?!); see attached. Makes me wonder....

SB 280 August 2002.pdf

[Mcstealth]

On ‎9‎/‎29‎/‎2018 at 8:32 AM, THill182 said:

PS: As I keep digging I also found a SB from 2002 applicable to M20R's of my serial number, relating to these very parts (?!); see attached. Makes me wonder....

SB 280 August 2002.pdf

Do not see a machined groove in the part on the SB illustration

Only an observation.

 

[takair]

On 9/29/2018 at 9:32 AM, THill182 said:

PS: As I keep digging I also found a SB from 2002 applicable to M20R's of my serial number, relating to these very parts (?!); see attached. Makes me wonder....

SB 280 August 2002.pdf

It does appear that at one time Mooney installed similar rod end with the locking tab and drilled nut.  Seems like yours was not done at the time.  Wonder if there are others out there?

[THill182]

8 hours ago, Mcstealth said:

Do not see a machined groove in the part on the SB illustration

Only an observation.

 

SB 280 calls for drilling a hole through the bolt to "secure it" (see below), which is not explained any further and surely will weaken this part. Also, the two nuts that secure that part should "jam" together, so shouldn't move at all I would think. But: No groove for sure. So it is strange...

 

[takair]

4 hours ago, THill182 said:

SB 280 calls for drilling a hole through the bolt to "secure it" (see below), which is not explained any further and surely will weaken this part. Also, the two nuts that secure that part should "jam" together, so shouldn't move at all I would think. But: No groove for sure. So it is strange...

 

No grooved bearing is the now discarded 915053-7 bearing.  I googled the NAS559-1 key and you will see it is the mystery locking tab that was in your original photo.  So, it seems that Mooney was installing these at some point and this SB was intended to reverse the install.  From the SB: 

"Cut safety wire of NAS559-1 Key and NAS509-4 Nut. Remove 915053-7 Bearings, and count the number of turns required to remove 915053-7 Bearing. This will simplify rigging of the landing gear later.

Discard 915053-7 Bearings, NAS509-4 Nuts and NAS559-1Keys."

[THill182]

OK; now I start to understand. Mooney did at one point install these, but they were replaced by the new part without groove.

Also: Here are more detailed pictures of the broken parts; this looks like over-stress to me (but I am not an engineer).

 

[Yetti]

Not and engineer but I have torn alot of stuff over the years.   Some how the rod has been pushing out an angle.  Most likely down where you see the paint on the tube scratched off by what looks like brake or fuel lines.   So something is/has been out of line.  The direction of out away from those couple of threads pulled.  Since the hemi was not extended very many threads it looks like the tube was too long.   If you have a picture of the other end of the tube and how it is attached that might help.

[takair]

1 hour ago, Yetti said:

Not and engineer but I have torn alot of stuff over the years.   Some how the rod has been pushing out an angle.  Most likely down where you see the paint on the tube scratched off by what looks like brake or fuel lines.   So something is/has been out of line.  The direction of out away from those couple of threads pulled.  Since the hemi was not extended very many threads it looks like the tube was too long.   If you have a picture of the other end of the tube and how it is attached that might help.

I was thinking the same.  Have seen the tube too long and end up bent under compression.  In this case, the bearing ended up failing.  I would check that the tube is not bent too.  Probably need to remove it and roll it on a flat surface.  Someone else mentioned that once out of alignment, all bets are off...I agree.